Method of transmitting and receiving downlink data and apparatus therefor

ABSTRACT

A method of receiving Downlink (DL) data by a User Equipment (UE) in a wireless communication system. The method includes: receiving information related to a number of repetitions of the DL data which is repeatedly transmitted in (i) at least one first Transmission Time Interval (TTI) included in a first subframe, and in (ii) at least one second TTI included in a second subframe that is after the first subframe; and receiving the DL data based on the number of repetitions of the DL data. If a Transmission Mode (TM) for the first subframe is different from a TM for the second subframe, then the UE does not receive the DL data in the at least one second TTI.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/710,489, filed on Dec. 11, 2019, which is a continuation of U.S.application Ser. No. 16/397,763, filed on Apr. 29, 2019, now U.S. Pat.No. 10,623,169, which claims the benefit of an earlier filing date andright of priority to U.S. Provisional Application No. 62/663,293, filedon Apr. 27, 2018, and U.S. Provisional Application No. 62/670,063, filedon May 11, 2018. The disclosures of the prior applications areincorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure generally relates to transmitting and receivingdownlink data in a wireless communication system.

BACKGROUND

As wireless communication technology faces increasing demands andexpectation of users and service providers, new technological evolutionis being developed to achieve future competitiveness. Specifically,techniques are being developed to achieve cost reduction per bit,increased service availability, flexible use of frequency bands, asimplified structure, an open interface, and appropriate powerconsumption.

SUMMARY

Systems and techniques are disclosed herein that are related totransmitting and receiving a downlink data channel.

One general aspect of the present disclosure includes a method ofreceiving downlink (DL) data by a user equipment (UE) in a wirelesscommunication system, the method including: receiving informationrelated to a number of repetitions of the DL data which is repeatedlytransmitted in (i) at least one first transmission time interval (TTI)included in a first subframe, and in (ii) at least one second TTIincluded in a second subframe that is after the first subframe; andreceiving the DL data based on the number of repetitions of the DL data,where, based on a transmission mode (TM) for the first subframe beingdifferent from a TM for the second subframe, the DL data is not receivedin the at least one second TTI. Other embodiments of this aspect includecorresponding computer systems, apparatus, and computer programsrecorded on one or more computer storage devices, each configured toperform the actions of the methods.

Implementations may include one or more of the following features. Themethod where the first subframe and the second subframe are consecutivein time. The method where the number of repetitions of the DL dataexceeds 1. The method where any one of the first subframe and the secondsubframe is a multicast broadcast single frequency network (MBSFN)subframe. The method may also include where the other one of the firstsubframe and the second subframe is a non-MBSFN subframe. The methodwhere a common reference signal (CRS)-based TM is configured for any oneof the first subframe and the second subframe. The method may alsoinclude where a demodulation reference signal (DMRS)-based TM isconfigured for the other one of the first subframe and the secondsubframe. The method where the information related to the number ofrepetitions of the DL data is included in cell-radio network temporaryidentifier (C-RNTI)-based downlink control information (DCI). The methodwhere the at least one first TTI and the at least one second TTI areshort TTIs. Implementations of the described techniques may includehardware, a method or process, or computer software on acomputer-accessible medium.

Another general aspect includes an apparatus including: at least oneprocessor; and at least one computer memory operably connectable to theat least one processor and storing instructions that, when executed bythe at least one processor, perform operations including: receivinginformation related to a number of repetitions of downlink (DL) datawhich is repeatedly transmitted in (i) at least one first transmissiontime interval (TTI) included in a first subframe, and in (ii) at leastone second TTI included in a second subframe that is located after thefirst subframe, and receiving the DL data based on the number ofrepetitions of the DL data, where, based on a transmission mode (TM) forthe first subframe being different from a TM for the second subframe,the DL data is not received in the at least one second TTI. Otherembodiments of this aspect include corresponding computer systems,apparatus, and computer programs recorded on one or more computerstorage devices, each configured to perform the actions of the methods.

Implementations may include one or more of the following features. Theapparatus where the first subframe and the second subframe areconsecutive in time. The apparatus where the number of repetitions ofthe DL data exceeds 1. The apparatus where any one of the first subframeand the second subframe is a multicast broadcast single frequencynetwork (MBSFN) subframe. The apparatus may also include where the otherone of the first subframe and the second subframe is a non-MBSFNsubframe. The apparatus where a common reference signal (CRS)-based TMis configured for any one of the first subframe and the second subframe.The apparatus may also include where a demodulation reference signal(DMRS)-based TM is configured for the other one of the first subframeand the second subframe. The apparatus where the information related tothe number of repetitions of the DL data is included in cell-radionetwork temporary identifier (C-RNTI)-based downlink control information(DCI). The apparatus where the at least one first TTI and the at leastone second TTI are short TTIs. Implementations of the describedtechniques may include hardware, a method or process, or computersoftware on a computer-accessible medium.

Another general aspect includes a method of transmitting downlink (DL)data by a base station (BS) in a wireless communication system, themethod including: transmitting information related to a number ofrepetitions of the DL data which is repeatedly transmitted in (i) atleast one first transmission time interval (TTI) included in a firstsubframe, and in (ii) at least one second TTI included in a secondsubframe that is located after the first subframe; and transmitting theDL data based on the number of repetitions of the DL data, where, basedon a transmission mode (TM) for the first subframe being different froma TM for the second subframe, the DL data is not transmitted in the atleast one second TTI. Other embodiments of this aspect includecorresponding computer systems, apparatus, and computer programsrecorded on one or more computer storage devices, each configured toperform the actions of the methods.

Another general aspect includes a user equipment (UE) configured toreceive downlink (DL) data in a wireless communication system, the UEincluding: at least one transceiver; at least one processor; and atleast one computer memory operably connectable to the at least oneprocessor and storing instructions that, when executed by the at leastone processor, perform operations including: receiving, through the atleast one transceiver, information related to a number of repetitions ofthe DL data which is repeatedly transmitted in (i) at least one firsttransmission time interval (TTI) included in a first subframe, and in(ii) at least one second TTI included in a second subframe that islocated after the first subframe; and receiving, through the at leastone transceiver, the DL data based on the number of repetitions of theDL data, where, based on a transmission mode (TM) for the first subframebeing different from a TM for the second subframe, the DL data is notreceived in the at least one second TTI. Other embodiments of thisaspect include corresponding computer systems, apparatus, and computerprograms recorded on one or more computer storage devices, eachconfigured to perform the actions of the methods.

Another general aspect includes a base station (BS) configured totransmit downlink (DL) data in a wireless communication system, the BSincluding: at least one transceiver; at least one processor; and atleast one computer memory operably connectable to the at least oneprocessor and storing instructions that, when executed by the at leastone processor, perform operations including: transmitting, through theat least one transceiver, information related to a number of repetitionsof the DL data which is repeatedly transmitted in (i) at least one firsttransmission time interval (TTI) included in a first subframe, and in(ii) at least one second TTI included in a second subframe that islocated after the first subframe; and transmitting, through the at leastone transceiver, the DL data based on the number of repetitions of theDL data, where, based on a transmission mode (TM) for the first subframebeing different from a TM for the second subframe, the DL data is nottransmitted in the at least one second TTI. The base station alsoincludes

Other embodiments of this aspect include corresponding computer systems,apparatus, and computer programs recorded on one or more computerstorage devices, each configured to perform the actions of the methods.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communication system;

FIGS. 2A and 2B illustrates an example of a control-plane protocol stackand a user-plane protocol stack in a radio interface protocolarchitecture between a user equipment (UE) and a radio access network;

FIG. 3 illustrates an example of physical channels and signaltransmission using the physical channels in a 3GPP system;

FIG. 4 illustrates an example of a structure of a radio frame;

FIG. 5 illustrates an example of a structure of a downlink radio frame;

FIGS. 6A and 6B illustrates an example of resource units used toconfigure a downlink control channel;

FIG. 7 illustrates an example of a structure of an uplink subframe;

FIG. 8 is a diagram illustrating an example of the structure of aMultimedia Broadcast Single Frequency Network (MBSFN) subframe;

FIGS. 9A and 9B are diagrams illustrating an example of the structure ofa short Transmission Time Interval (TTI);

FIGS. 10A and 10B are diagrams illustrating examples of repeatedlytransmitted data which is scheduled;

FIGS. 11 to 13 are diagrams illustrating examples of operations of a UE,a BS, and a network according to some implementations of the presentdisclosure;

FIG. 14 is a diagram illustrating an example of data which is repeatedlytransmitted in subframes configured as different transmission modes(TMs) and/or types, according to some implementations of the presentdisclosure; and

FIG. 15 is a block diagram of an example of wireless devices forimplementing the present disclosure.

DETAILED DESCRIPTION

Implementations are disclosed herein that enable transmitting andreceiving downlink data, and more particularly, transmitting andreceiving repeatedly-transmitted data in consecutive subframes inscenarios where the consecutive subframes are configured as differentsubframe types and/or different transmission modes (TMs).

As an example, in some scenarios, repeated transmissions of data may bescheduled so as to span over multiple subframes of different typesand/or different TMs. In such scenarios, a problem may arise if aReference Signal (RS) is present in one subframe, but is not present inanother subframe in which the data subsequently repeated. Compoundingthis problem, the two subframes may have different types and/ordifferent TMs. In such scenarios, the UE may fail to perform decodingfor the one or more of the repeated transmissions of data in subsequentsubframes having different types and/or different TMs.

Implementations disclosed herein address such problems. According tosome implementations, a User Equipment (UE) receives information relatedto a number of repetitions of the DL data which is repeatedlytransmitted in (i) at least one first Transmission Time Interval (TTI)included in a first subframe, and in (ii) at least one second TTIincluded in a second subframe that is after the first subframe. The UEthen receives the DL data based on the number of repetitions of the DLdata. If a Transmission Mode (TM) for the first subframe is differentfrom a TM for the second subframe, then the UE does not receive the DLdata in the at least one second TTI.

According to implementations of the present disclosure, data which isrepeatedly transmitted in subframes that are configured as differentsubframe types and/or different TMs can be efficiently transmitted andreceived.

Reference will now be made in detail to various implementations of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

The configuration, operation, and other features of the presentdisclosure will readily be understood with implementations of thepresent disclosure described with reference to the attached drawings.Embodiments of the present disclosure as set forth herein are examplesin which the technical features of the present disclosure are applied toa 3rd Generation Partnership Project (3GPP) system.

While implementations of the present disclosure are described in thecontext of Long Term Evolution (LTE) and LTE-Advanced (LTE-A) systems,they are purely exemplary. Therefore, the implementations of the presentdisclosure are applicable to any other communication system as long asthe above definitions are valid for the communication system. Inaddition, while implementations of the present disclosure are describedin the context of Frequency Division Duplexing (FDD), they are alsoreadily applicable to Half-FDD (H-FDD) or Time Division Duplexing (TDD)with some modifications.

A brief description will be given of a 3rd Generation PartnershipProject Long Term Evolution (3GPP LTE) system as an example of awireless communication system to which the present disclosure can beapplied.

FIG. 1 illustrates an example of a configuration of a wirelesscommunication system. In some scenarios, this example may be used toimplement an Evolved Universal Mobile Telecommunications System (E-UMTS)network.

The E-UMTS system is an evolution of a UMTS system. E-UMTS is alsoreferred to as an LTE system. Details of the technical specifications ofUMTS and E-UMTS can be found in Release 7 and Release 8 of “3rdGeneration Partnership Project; Technical Specification Group RadioAccess Network”, respectively.

Referring to FIG. 1, the E-UMTS system includes a User Equipment (UE),an evolved Node B (eNode B or eNB), and an Access Gateway (AG) which islocated at an end of an Evolved UMTS Terrestrial Radio Access Network(E-UTRAN) and connected to an external network. The eNB may transmitmultiple data streams simultaneously, for broadcast service, multicastservice, and/or unicast service.

A single eNB manages one or more cells. A cell is set to operate in oneof the bandwidths of 1.25, 2.5, 5, 10, 15 and 20 MHz and providesDownlink (DL) or Uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be configured so as to providedifferent bandwidths. An eNB controls data transmission and reception toand from a plurality of UEs. Regarding DL data, the eNB notifies aparticular UE of a time-frequency area in which the DL data is supposedto be transmitted, a coding scheme, a data size, Hybrid Automatic RepeatreQuest (HARQ) information, etc., by transmitting DL schedulinginformation to the UE. Regarding UL data, the eNB notifies a particularUE of a time-frequency area in which the UE can transmit data, a codingscheme, a data size, HARQ information, etc., by transmitting ULscheduling information to the UE. An interface for transmitting usertraffic or control traffic may be defined between eNBs. A Core Network(CN) may include an AG and a network node for user registration of UEs.The AG manages the mobility of UEs on a Tracking Area (TA) basis. A TAincludes a plurality of cells.

FIGS. 2A and 2B illustrates an example of control-plane and user-planeprotocol stacks in a radio interface protocol architecture between auser equipment (UE) and a radio access network. In some scenarios, thisexample may conform to a 3GPP wireless access network standard between aUE and an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN).

For example, the control plane is a path in which the UE and the E-UTRANtransmit control messages to manage calls, and the user plane is a pathin which data generated from an application layer, for example, voicedata or Internet packet data is transmitted.

A PHYsical (PHY) layer at Layer 1 (L1) provides information transferservice to its higher layer, a Medium Access Control (MAC) layer. ThePHY layer is connected to the MAC layer via transport channels. Thetransport channels deliver data between the MAC layer and the PHY layer.Data is transmitted on physical channels between the PHY layers of atransmitter and a receiver. The physical channels use time and frequencyas radio resources. Specifically, the physical channels are modulated inOrthogonal Frequency Division Multiple Access (OFDMA) for Downlink (DL)and in Single Carrier Frequency Division Multiple Access (SC-FDMA) forUplink (UL).

The MAC layer at Layer 2 (L2) provides service to its higher layer, aRadio Link Control (RLC) layer via logical channels. The RLC layer at L2supports reliable data transmission. RLC functionality may beimplemented in a function block of the MAC layer. A Packet DataConvergence Protocol (PDCP) layer at L2 performs header compression toreduce the amount of unnecessary control information and thusefficiently transmit Internet Protocol (IP) packets such as IP version 4(IPv4) or IP version 6 (IPv6) packets via an air interface having anarrow bandwidth.

A Radio Resource Control (RRC) layer at the lowest part of Layer 3 (orL3) is defined only on the control plane. The RRC layer controls logicalchannels, transport channels, and physical channels in relation toconfiguration, reconfiguration, and release of radio bearers. A radiobearer refers to a service provided at L2, for data transmission betweenthe UE and the E-UTRAN. For this purpose, the RRC layers of the UE andthe E-UTRAN exchange RRC messages with each other. If an RRC connectionis established between the UE and the E-UTRAN, the UE is in RRCConnected mode and otherwise, the UE is in RRC Idle mode. A Non-AccessStratum (NAS) layer above the RRC layer performs functions includingsession management and mobility management.

DL transport channels used to deliver data from the E-UTRAN to UEsinclude a Broadcast Channel (BCH) carrying system information, a PagingChannel (PCH) carrying a paging message, and a Shared Channel (SCH)carrying user traffic or a control message. DL multicast traffic orcontrol messages or DL broadcast traffic or control messages may betransmitted on a DL SCH or a separately defined DL Multicast Channel(MCH). UL transport channels used to deliver data from a UE to theE-UTRAN include a Random Access Channel (RACH) carrying an initialcontrol message and a UL SCH carrying user traffic or a control message.Logical channels that are defined above transport channels and mapped tothe transport channels include a Broadcast Control Channel (BCCH), aPaging Control Channel (PCCH), a Common Control Channel (CCCH), aMulticast Control Channel (MCCH), a Multicast Traffic Channel (MTCH),etc.

FIG. 3 illustrates examples of physical channels and transmittingsignals on the physical channels in a 3GPP system.

Referring to FIG. 3, when a UE is powered on or enters a new cell, theUE performs initial cell search (S301). The initial cell search involvesacquisition of synchronization to an eNB. Specifically, the UEsynchronizes its timing to the eNB and acquires a cell Identifier (ID)and other information by receiving a Primary Synchronization Channel(P-SCH) and a Secondary Synchronization Channel (S-SCH) from the eNB.Then the UE may acquire information broadcast in the cell by receiving aPhysical Broadcast Channel (PBCH) from the eNB. During the initial cellsearch, the UE may monitor a DL channel state by receiving a DownLinkReference Signal (DL RS).

After the initial cell search, the UE may acquire detailed systeminformation by receiving a Physical Downlink Control Channel (PDCCH) andreceiving a Physical Downlink Shared Channel (PDSCH) based oninformation included in the PDCCH (S302).

If the UE initially accesses the eNB or has no radio resources forsignal transmission to the eNB, the UE may perform a random accessprocedure with the eNB (S303 to S306). In the random access procedure,the UE may transmit a predetermined sequence as a preamble on a PhysicalRandom Access Channel (PRACH) (S303 and S305) and may receive a responsemessage to the preamble on a PDCCH and a PDSCH associated with the PDCCH(S304 and S306). In the case of a contention-based RACH, the UE mayadditionally perform a contention resolution procedure.

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S307) and transmit a Physical Uplink Shared Channel(PUSCH) and/or a Physical Uplink Control Channel (PUCCH) to the eNB(S308), which is a general DL and UL signal transmission procedure.Particularly, the UE receives Downlink Control Information (DCI) on aPDCCH. Herein, the DCI includes control information such as resourceallocation information for the UE. Different DCI formats are definedaccording to different usages of DCI.

Control information that the UE transmits to the eNB on the UL orreceives from the eNB on the DL includes a DL/UL ACKnowledgment/NegativeACKnowledgment (ACK/NACK) signal, a Channel Quality Indicator (CQI), aPrecoding Matrix Index (PMI), a Rank Indicator (RI), etc. In the 3GPPLTE system, the UE may transmit control information such as a CQI, aPMI, an RI, etc. on a PUSCH and/or a PUCCH.

FIG. 4 illustrates an example of a structure of a radio frame. In somescenarios, such implementations may be compatible with an LTE system.

Referring to FIG. 4, a radio frame is 10 ms (327200×T_(s)) long anddivided into 10 equal-sized subframes. Each subframe is 1 ms long andfurther divided into two slots. Each time slot is 0.5 ms (15360×T_(s))long. Herein, T_(s) represents a sampling time and T_(s)=1/(15kHz×2048)=3.2552×10′ (about 33 ns). A slot includes a plurality ofOrthogonal Frequency Division Multiplexing (OFDM) symbols or SC-FDMAsymbols in the time domain by a plurality of Resource Blocks (RBs) inthe frequency domain. In the LTE system, one RB includes 12 subcarriersby 7 (or 6) OFDM symbols. A unit time during which data is transmittedis defined as a Transmission Time Interval (TTI). The TTI may be definedin units of one or more subframes. The above-described radio framestructure is merely exemplary and thus the number of subframes in aradio frame, the number of slots in a subframe, or the number of OFDMsymbols in a slot may vary.

FIG. 5 illustrates examples of control channels included in a controlregion of a subframe in a DL radio frame. In some scenarios, suchimplementations may be compatible with an LTE system.

Referring to FIG. 5, a subframe includes 14 OFDM symbols. The first oneto three OFDM symbols of a subframe are used for a control region andthe other 13 to 11 OFDM symbols are used for a data region according toa subframe configuration. In FIG. 5, reference characters R1 to R4denote RSs or pilot signals for antenna 0 to antenna 3. RSs areallocated in a predetermined pattern in a subframe irrespective of thecontrol region and the data region. A control channel is allocated tonon-RS resources in the control region and a traffic channel is alsoallocated to non-RS resources in the data region. Control channelsallocated to the control region include a Physical Control FormatIndicator Channel (PCFICH), a Physical Hybrid-ARQ Indicator Channel(PHICH), a Physical Downlink Control Channel (PDCCH), etc.

The PCFICH is a physical control format indicator channel carryinginformation about the number of OFDM symbols used for PDCCHs in eachsubframe. The PCFICH is located in the first OFDM symbol of a subframeand configured with priority over the PHICH and the PDCCH. The PCFICHincludes 4 Resource Element Groups (REGs), each REG being distributed tothe control region based on a cell Identity (ID). One REG includes 4Resource Elements (REs). An RE is a minimum physical resource defined byone subcarrier by one OFDM symbol. The PCFICH is set to 1 to 3 or 2 to 4according to a bandwidth. The PCFICH is modulated in Quadrature PhaseShift Keying (QPSK).

The PHICH is a physical Hybrid-Automatic Repeat and request (HARQ)indicator channel carrying an HARQ ACK/NACK for a UL transmission. Thatis, the PHICH is a channel that delivers DL ACK/NACK information for ULHARQ. The PHICH includes one REG and is scrambled cell-specifically. AnACK/NACK is indicated in one bit and modulated in Binary Phase ShiftKeying (BPSK). The modulated ACK/NACK is spread with a Spreading Factor(SF) of 2 or 4. A plurality of PHICHs mapped to the same resources forma PHICH group. The number of PHICHs multiplexed into a PHICH group isdetermined according to the number of spreading codes. A PHICH (group)is repeated three times to obtain a diversity gain in the frequencydomain and/or the time domain.

The PDCCH is a physical DL control channel allocated to the first n OFDMsymbols of a subframe. Herein, n is an integer greater than or equal to1, and is indicated by the PCFICH. The PDCCH occupies one or more CCEs.The PDCCH carries resource allocation information about transportchannels, PCH and DL-SCH, a UL scheduling grant, and HARQ information toeach UE or UE group. The PCH and the DL-SCH are transmitted on a PDSCH.Therefore, an eNB and a UE transmit and receive data usually on thePDSCH, except for specific control information or specific service data.

Information indicating one or more UEs to receive PDSCH data andinformation indicating how the UEs are supposed to receive and decodethe PDSCH data are delivered on a PDCCH. For example, in scenarios wherethe Cyclic Redundancy Check (CRC) of a specific PDCCH is masked by RadioNetwork Temporary Identity (RNTI) “A” and information about datatransmitted in radio resources (e.g., at a frequency position) “B” basedon transport format information (e.g., a transport block size, amodulation scheme, coding information, etc.) “C” is transmitted in aspecific subframe, a UE within a cell monitors, e.g., blind-decodes, aPDCCH using its RNTI information in a search space. If one or more UEshave RNTI “A”, then those UEs receive the PDCCH and receive a PDSCHindicated by “B” and “C” based on information of the received PDCCH.

FIGS. 6A and 6B illustrates examples of resource units used to configurea downlink control channel. In some scenarios, such implementations maybe compatible with an LTE system.

FIG. 6A shows a case in which the number of transmit (Tx) antennas is 1or 2 and FIG. 6B shows a case in which the number of Tx antenna is 4.Although a different RS pattern is used according to the number of Txantennas, REs are configured for a DL control channel in the samemanner.

Referring to FIGS. 6A and 6B, a basic resource unit of a DL controlchannel is an REG. The REG includes four contiguous REs except for REscarrying RSs. REGs are delineated with bold lines in FIGS. 6A and 6B. APCFICH and a PHICH include 4 REGs and 3 REGs, respectively. A PDCCH isconfigured in units of a control channel element (CCE), each CCEincluding 9 REGs.

To determine whether a PDCCH including L CCEs is transmitted to a UE,the UE is configured to monitor M^((L)) (≥L) CCEs that are arrangedcontiguously or according to a predetermined rule. The value of L thatthe UE should consider for PDCCH reception may be a plural value. TheCCE sets that the UE should monitor to receive a PDCCH are referred toas a search space. As an example, a system that is compatible with LTEmay define search spaces as illustrated in Table 1, below.

TABLE 1 Number of Search space S_(k) ^((L)) PDCCH Aggregation levelcandidates Type L Size [in CCEs] M^((L)) UE- 1 6 6 specific 2 12 6 4 8 28 16 2 Common 4 16 4 8 16 2

In the example of Table 1, the parameter L is a CCE aggregation level,that is, the number of CCEs in a PDCCH, the parameter S_(k) ^((L)) is asearch space with CCE aggregation level L, and the parameter M^((L)) isthe number of candidate PDCCHs to be monitored in the search space withCCE aggregation level L.

Search spaces are classified into a UE-specific search space accessibleonly by a specific UE and a common search space accessible by all UEswithin a cell. A UE monitors common search spaces with CCE aggregationlevels 4 and 8 and UE-specific search spaces with CCE aggregation levels1, 2, 4, and 8. A common search space and a UE-specific search space mayoverlap each other.

For each CCE aggregation level, the position of the first CCE (a CCEhaving the smallest index) of a PDCCH search space allocated to a UEchanges every subframe. This is called PDCCH search space hashing.

A CCE may be distributed across a system band. More specifically, aplurality of logically contiguous CCEs may be input to an interleaverand the interleaver may permute the sequence of the input CCEs on an REGbasis. Accordingly, the time/frequency resources of one CCE aredistributed physically across the total time/frequency region of thecontrol region of a subframe. As a control channel is configured inunits of a CCE but interleaved in units of an REG, frequency diversitygain and interference randomization gain may be maximized.

FIG. 7 illustrates an example of a structure of a UL subframe. In somescenarios, such implementations may be compatible with an LTE system.

Referring to FIG. 7, a UL subframe may be divided into a control regionand a data region. A Physical Uplink Control Channel (PUCCH) includingUplink Control Information (UCI) is allocated to the control region anda Physical uplink Shared Channel (PUSCH) including user data isallocated to the data region. The middle of the subframe is allocated tothe PUSCH, while both sides of the data region in the frequency domainare allocated to the PUCCH. Control information transmitted on the PUCCHmay include an HARQ ACK/NACK, a CQI representing a downlink channelstate, an RI for Multiple Input Multiple Output (MIMO), a SchedulingRequest (SR) requesting UL resource allocation. A PUCCH for one UEoccupies one RB in each slot of a subframe. That is, the two RBsallocated to the PUCCH are frequency-hopped over the slot boundary ofthe subframe. Particularly, PUCCHs with m=0, m=1, and m=2 are allocatedto a subframe in the example of FIG. 7.

FIG. 8 is a diagram illustrating an example of the structure of aMultimedia Broadcast Single Frequency Network (MBSFN) subframe.

Referring to the upper part of FIG. 8, a single frame may include 10subframes, which may include two types of subframes: (i) non-MBSFNsubframes, which are used for normal (e.g., unicast) data transmissionand reception, and (ii) MBSFN subframes, which may be used for broadcastor multicast data transmission. In some implementations, a non-MBSFNsubframe and an MBSFN subframe differ in the number of OFDM symbols, thelength of a Cyclic Prefix (CP), and the structure and number ofCell-specific Reference Signals (CRSs).

In some implementations, such as those compatible with LTE-Rel 8 andLTE-Rel 9, the MBSFN subframes may be used only for the purpose oftransmitting broadcast or multicast data.

However, in other implementations, such as those compatible with LTE-Rel10 or beyond, the MBSFN subframe may also be used for unicast datatransmission, which is data transmission for a specific UE, in additionto the purpose of broadcast or multicast data transmission.

Referring to the lower part of FIG. 8, an MBSFN subframe is a type ofsubframe for transmitting a Physical Broadcast Channel (PBCH). An MBSFNsubframe may be a type of subframe in which a CRS is not transmitted ina region other than a PDCCH region including the first two OFDM symbols.In this case, the PDCCH region may include one OFDM symbol. In someimplementations, a UE for which data reception in the MBSFN subframe isnot configured may not receive DL data in a region other than the PDCCHregion included in the MBSFN subframe. MBSFN configuration informationmay represent information for configuring the MBSFN subframe and may betransmitted through a higher layer signal. For example, a Base Station(BS) may transmit the MBSFN configuration information through SystemInformation Block 2 (SIB-2) transmitted on a PDSCH. The MBSFNconfiguration information may include information such as a bitmapindicating the MBSFN subframe, a radio frame allocation period, a radioframe allocation offset, and subframe allocation.

An example of transmitting and receiving a DL data channel according tosome implementations of the present disclosure is described below.

Implementations disclosed herein enable, in some scenarios, transmittingand receiving information while achieving very low latency and very highreliability. To this end, techniques for configuring various targetQuality of Service (QoS) requirements such as latency and/or reliabilityand efficiently providing services satisfying the target QoSrequirements by differently performing an operation according to eachtarget QoS requirement may be utilized.

The present disclosure describes implementations that, in somescenarios, enable for repeatedly transmitting DL data, by the BS to theUE, to achieve higher reliability and lower latency in a cellularcommunication system. Particularly, the present disclosure describesimplementations for repeatedly transmitting the DL data in scenarioswhere repeated transmission of the DL data is scheduled so as to spanmultiple subframes of different types and/or different transmissionmodes (TMs).

Although features and/or implementations of the present disclosure maybe regarded as one technique, a combination of features and/orimplementations disclosed herein may also be utilized. In addition,features and implementations disclosed herein are not limited to theparticular examples disclosed herein, nor are they limited to beingapplied to a specific system. Instead, the feature and implementationsdisclosed herein may be extended in the range which is easily derivablefrom an implementation proposed in the present disclosure by thoseskilled in the art and the implementations of the present disclosure areapplicable to various communication systems such as LTE, LTE-A, LTE-Pro,NR, and IEEE systems.

In addition, some or all parameters of the present disclosure, some orall operations of the present disclosure, a combination of parametersand/or operations, whether a corresponding parameter and/or operation isapplied, and/or whether a combination of parameters and/or operations isapplied may be indicated by the BS to the UE through higher layersignaling and/or physical layer signaling, or may be predefined in asystem.

Implementations of the present disclosure described in relation todifferent subframe types may also be applied to different TransmissionModes (TMs). For example, implementations of the present disclosure maybe applied where two subframes have the same subframe type, but havedifferent TMs.

As described herein, a Transmission Time Interval (TTI) may correspondto various TTI length units, such as a subslot/slot/subframe. A subslotand a slot may be referred to as a “short TTI.” In some implementations,a short TTI may be defined as having a duration that is smaller than 1ms of a Downlink Shared Channel (DL-SCH) and an Uplink Shared Channel(UL-SCH). In some implementations, control channels supporting the shortTTI, for example, a Short PDCCH (SPDCCH) and a Short PUCCH (SPUCCH), mayalso be transmitted in a duration shorter than 1 ms. In this case, aslot has a duration of 0.5 ms and, therefore, may include 7 symbols. Insome implementations, a subslot may include two symbols or threesymbols.

In a TDD system, short TTI-based transmission may be performed in unitsof slots and, in an FDD system, short TTI-based transmission may beperformed in units of slots and/or subslots.

In this case, one subframe may include 6 subslots and a pattern in whichthe subslots are deployed may differ according to the number of symbolsused for a PDCCH. For example, if the number of symbols used for thePDCCH is 1 or 3, then each of subslot 0 and subslot 5 includes 3 symbolsand each of the other subslots includes 2 symbols, as illustrated inFIG. 9A.

As another example, if the number of symbols used for the PDCCH is 2,then each of subslot 1 and subslot 5 includes 3 symbols and each of theother subslots includes 2 symbols, as illustrated in FIG. 9B.

In some implementations, data may be repeatedly transmitted. This may bedone, for example, to increase reliability of DL transmission.

For example, as shown in FIG. 10A, a control channel and a data channelscheduled by the control channel may be independently transmitted inevery TTI. The BS may inform the UE that data channels transmitted in aplurality of TTIs carry the same Transmission Block (TB), using a HARQprocess number or a New Data Indicator (NDI) in each control channel andrepeatedly transmit the same data in the plural TTIs.

As another example, as shown in FIG. 10B, a control channel that istransmitted in a single TTI may schedule data which is repeatedlytransmitted in a plurality of TTIs. That is, the control channeltransmitted in a single TTI may schedule data for a plurality of TTIs.This may be done, for example, to further reduce overhead of the controlchannel as compared with the example in FIG. 10A.

Thus, the control channel may be transmitted in a plurality of TTIs and,in this case, the number of TTIs in which the control channel istransmitted may be fewer than the number of TTIs in which the datachannel is transmitted. Information such as a Modulation and CodingScheme (MCS)/Resource Allocation (RA) in Downlink Control Information(DCI) for scheduling data which is repeatedly transmitted in a pluralityof TTIs may be equally applied to all TTIs in which data is repeatedlytransmitted. The DCI may include information about the number ofrepeated transmissions of data.

In some implementations, such as those compatible with an LTE Short TTI(sTTI) system, a different TM may be configured per subframe type.Specifically, different TMs may be configured for an MBSFN subframe andfor a non-MBSFN subframe. For example, TM 4 may be configured for anon-MBSFN subframe and TM 9 may be configured for an MBSFN subframe. TheTTIs (i.e., sTTIs) that are included in a subframe, which is configuredas a specific subframe type, may operate based on a TM configured incorrespondence to the specific subframe type.

If data which is repeatedly transmitted in a plurality of TTIs includinga specific TTI is scheduled through DCI transmitted in the specific TTIas described above, then information about the number k of repeatedtransmissions of the data may be transmitted, for example through theDCI.

If decoding of the DCI is successful, then the UE may be configured notto attempt to decode the DCI in the other (k−1) continuous (ordiscontinuous) TTIs in which the data is repeatedly transmitted, or theUE may be configured to discard the DCI even if the UE has detected theDCI by attempting to decoding the DCI. The DCI that the UE does notdecode or discards may be DCI related to Cell-RNTI (C-RNTI)-based datascheduling or DCI related to DL data scheduling. The DCI that the UE hassuccessfully decoded may also be the DCI related to C-RNTI-based datascheduling or the DCI related to DL data scheduling.

In some scenarios, repeated transmissions of data may be scheduled bysuccessfully decoded DCI so as to span over multiple subframes ofdifferent types (e.g., an MBSFN subframe and a non-MBSFN subframe)and/or different TMs. In such scenarios, a problem may arise in that aReference Signal (RS) for data decoding in one subframe (in which thesuccessfully decoded DCI is transmitted) may not be present in anothersubframe that includes a part or all of subsequent repeated transmissionof that data. Compounding this problem, the two subframes may havedifferent types and/or different TMs. In such scenarios, the UE may failto perform decoding for one or more of the repeated transmissions ofdata in subsequent subframes having different types and/or differentTMs.

As an example, consider a scenario where one subframe (in which thesuccessfully decoded DCI is transmitted) is a non-MBSFN subframe, and TM4 is configured in that non-MBSFN subframe, with a Common ReferenceSignal (CRS) being used. In such scenarios, if another subframe (inwhich a part or all of subsequent repeated transmission of data isincluded) is an MBSFN subframe and TM 9 is configured in that otherMBSFN subframe, then the CRS is not present in that other MBSFNsubframe. In such scenarios, that the UE may fail to decode therepeatedly transmitted data in the other MBSFN subframe, which lacks theCRS.

Generally, applied references signals (RSs) may differ according todifferent subframe types and/or different TMs configured in subframeshaving different subframe types. If DCI formats for scheduling differentTMs configured in subframes of different types differ, then fieldconfigurations and/or field information of the DCI formats aredifferently configured.

Accordingly, if data which is repeatedly transmitted in TTIs (includingan initial TTI and at least one subsequent TTI) is scheduled through DCItransmitted in the initial TTI, and if the DCI is successfully decoded(so that DCI is not decoded in the subsequent TTIs or is discarded),then the UE may fail to acquire information (such as precoding/rankinformation) that should be provided for a TM configured according to achanged subframe type (even though data is repeatedly transmitted oversubframe types of which are differently configured). Accordingly,problems may arise in which the UE cannot normally decode one or more(or parts of) repeated transmission for a specific TB that istransmitted in a subsequent subframe.

Implementations of the present disclosure may, in some scenarios,address such problems.

Prior to description of the implementations, an example of an operationof a UE and a BS according to implementations of the present disclosurewill now be described with reference to FIGS. 11 to 13.

FIG. 11 is a diagram illustrating an example of operations of a UEaccording to implementations of the present disclosure. Referring toFIG. 11, the UE may receive (i) first information for configuring a typeof each of subframes and (ii) second information for configuring a TMapplied to each of the subframes (S1101). The first information and thesecond information may be received through higher layer signaling and/orphysical layer signaling. Then, the UE decodes DCI related to repeatedtransmission of data in a specific TTI, specifically, in an sTTI(S1103). The DCI may include information about the number of repeatedtransmissions of the data and information about an MCS, RA, precoding,and rank, for a type and a TM configured in a subframe in which the DCIis included.

Upon detecting the DCI, the UE may receive the repeatedly transmitteddata over subframes configured as different types and/or different TMs,based on the information included in the DCI, the first information, andthe second information (S1105).

A detailed operation method of receiving the repeatedly transmitted databy the UE based on the detected DCI, the first information, and thesecond information may conform to implementations which will bedescribed further below.

FIG. 12 illustrates an example of operations of a BS according to someimplementations of the present disclosure. Referring to FIG. 12, the BSmay transmit (i) first information for configuring a type of each ofsubframes, and (ii) second information for configuring a TM applied toeach of the subframes (S1201). The first information and the secondinformation may be transmitted through higher layer signaling and/orphysical layer signaling. Then, the BS may transmit DCI related torepeated transmission of data in a specific TTI, specifically, in ansTTI (S1203). The DCI may include information about the number ofrepeated transmissions of the data and information about an MCS, RA,precoding, and rank, for a type and a TM configured in a subframe inwhich the DCI is included.

Upon transmitting the DCI, the BS may repeatedly transmit the data oversubframes configured as different types and/or different TMs, based onthe information included in the DCI, the first information, and thesecond information (S1205).

Further examples are provided below of a BS repeatedly transmitting thedata over subframes configured as different types and/or different TMsbased on the transmitted DCI, the first information, and the secondinformation.

FIG. 13 illustrates an example of operations of a UE and a BS in termsof an entire network. As shown in this example, the BS may transmit (i)first information for configuring a type of each of subframes and (ii)second information for configuring a TM applied to each of the subframesto the UE through higher layer signaling and/or physical layer signaling(S1301). Next, the BS may transmit DCI related to repeated transmissionof data in a specific TTI, specifically, in a specific sTTI, to the UE(S1303). The DCI may include information about the number of repeatedtransmissions of the data and information about an MCS, RA, precoding,and rank, for a type and a TM configured in a subframe in which the DCIis included.

Upon transmitting the DCI, the BS may repeatedly transmit data oversubframes configured as different types and/or different TMs, based onthe information included in the DCI, the first information, and thesecond information and the UE may receive the repeatedly transmitteddata based on the DCI, the first information, and the second information(S1305).

Further examples are provided below of a BS repeatedly transmitting dataover subframes configured as different types and/or different TMs, basedon the DCI, the first information, and the second information, and a UEreceiving the repeatedly transmitted data.

Next, some examples of implementations for performing the operations ofthe UE and the BS will be described.

FIG. 14 is a diagram illustrating an example of data which is repeatedlytransmitted in subframes configured as different transmission modes(TMs) and/or types, according to some implementations of the presentdisclosure.

However, the example described below with reference to FIG. 14 is merelyto aid in understanding the present disclosure, and implementations ofthe present disclosure are not limited to the example in FIG. 14. Thepresent disclosure may also be applied to other numbers of repeatedtransmissions, other types of subframes in which repeatedly transmittedTTIs (or repeatedly transmitted data) are included, and/or otherconfigurations of TMs.

In the example of FIG. 14, the UE decodes, in TTI #n, DCI indicating thenumber, 4, of repeated transmissions. Furthermore, TTI #n and TTI #n+1(in which data is repeatedly transmitted) are included in a subframe oftype A (and/or TM A). Furthermore, TTI #n+2 and TTI #n+3 (in which datais repeatedly transmitted) are included in a subframe of type B (and/orTM B). More specifically, the subframe of type A may be an MBSFNsubframe and TM A may be TM 9. In addition, the subframe of type B maybe a non-MBSFN subframe and TM B may be TM 4.

In this example, the BS additionally transmits DCI for a TM configuredin a subframe of type B in TTI #n+2 and the UE may attempt to decode theadditionally transmitted DCI. This may be an exception to the case inwhich, if the UE succeeds in decoding DCI transmitted in a specific TTIfor scheduling the repeatedly transmitted data, the UE does not attemptto decode DCI transmitted in a subsequent TTI (e.g., DCI related toC-RNTI-based data scheduling) or discards the DCI even when the UEdetects the DCI by attempting to perform decoding.

Herein, scheduling information such as precoding/rank, included in theDCI decoded in TTI #n+2, may be equally applied to data transmission inTTI #n+2 and TTI #n+3. More generally, if plural TTIs to which repeatedtransmissions of the data (scheduled by successfully decoded DCI) belongare included in different subframes, and if TMs of the differentsubframes are changed due to change in types of the subframes, then theUE may additionally detect decoding of the DCI in a TTI included in asubsequent subframe having a changed TM and/or type. The UE may thenattempt to decode the repeatedly transmitted data in those subsequentTTIs (including a TTI in which the DCI included in the subframe havingthe changed TM and/or type is detected) according to an operationindicated by the DCI. In some scenarios, a TTI in which the UE attemptsto decode the DCI in a subsequent subframe may be the first TTI ofsubsequent subframes.

In scenarios of combinations of partial TMs, the UE may not decode theDCI in a TTI included in a subsequent subframe even if a TM is changedaccording to a corresponding combination while data is repeatedlytransmitted. For example, the UE may omit an operation of decoding theDCI in the first TTI of the subsequent subframe.

Whether this operation is performed may be predefined in a system or maybe indicated to the UE by the BS through higher layer signaling and/orphysical layer signaling.

The above operation may be performed such that two DCIs are transmittedin two subframes, respectively, where the two subframes are configuredwith different TMs and/or different types in a duration in which thedata is repeatedly transmitted. In this case, the BS may indicate, tothe UE, that one or more TTIs corresponding to the number of repeatedtransmissions of data indicated by the first DCI may include one or moreTTIs corresponding to the number of repeated transmissions of dataindicated by the second DCI.

For example, referring back to the example of FIG. 14, if DCItransmitted in TTI #n indicates the number, k, of repeated transmissionsof data, then the data is repeatedly transmitted in TTI #n to TTI#n+(k−1). If TTIs starting from TTI #n+p (where p<k−1) are included in asubframe configured as a different TM and/or a type different from a TMand/or a type of an initial TTI, then DCI may be transmitted in TTI #n+pand the UE may operate to decode the DCI.

In this case, the number of repeated transmissions of data indicated bythe DCI transmitted in TTI #n+p may be a value smaller than or equal tok-p. Alternatively, under the assumption that the number of repeatedtransmissions of data indicated by the DCI transmitted in TTI #n+p isk-p, a specific value which is predefined or is indicated by the BS tothe UE through higher layer signaling and/or physical layer signalingmay be transmitted in a field for indicating the number of repeatedtransmissions of data in the DCI and the specific value may be used as avirtual Cyclic Redundancy Check (CRC).

In addition, the BS may indicate the number of repeated transmissions ofdata in consideration of a boundary between subframes at which a TMand/or a subframe type is changed or a boundary between subframes havingthe same TM and/or subframe type. In this case, whether data which isrepeatedly transmitted over the boundary between subframes at which a TMand/or a subframe type is changed or the boundary between subframeshaving the same TM and/or subframe type is combined may be predefined ina system or may be indicated by the BS to the UE through higher layersignaling and/or physical layer signaling.

For example, if it is necessary to indicate 4 repeated transmissions ofdata at a timing of TTI #n and a subframe type and/or a TM is changedstarting from TTI #n+2, then the BS may indicate the number, 2, ofrepeated transmissions of data through DCI transmitted at a timing ofTTI #n and may indicate the number, 2, of repeated transmissions ofdata, through the DCI transmitted at a timing of TTI #n+2, together withthe same HARQ process ID and/or non-toggled NDI as a HARQ process IDand/or a non-toggled NDI of the previously transmitted DCI. If combiningrepeatedly transmitted data over two subframes is indicated or ispredefined, then the UE may combine a total of 4 repeated transmissionsof the data, twice per type and/or TM and transmit HARQ-ACK for the databased on a timing at which all of data repeatedly transmitted over asubframe boundary is received.

The BS may predefine scheduling information such as precoding/rank to beapplied to repeated transmission of data in TTIs #n+2 and #n+3 of asubframe of type B in the system or signal the scheduling information tothe UE through higher layer signaling and/or physical layer signaling.In this case, as opposed to the above description, additional DCI neednot be transmitted in TTI #n+2. For example, if a TM and/or a subframetype is changed from a CRS-based TM and/or a non-MBSFN subframe to aDMRS-based TM and/or an MBSFN subframe, then information such as ascrambling ID, the number of layers, an antenna port, and a PDSCH ratematching and Quasi co-location Indicator (PQI) may be implemented. Adefault state or a configuration for the information may be predefinedin the system or may be indicated by the BS to the UE through higherlayer signaling and/or physical layer signaling. Alternatively, DCIreceived during scheduling of the latest DMRS-based TM and/or MBSFNsubframe may be reused.

Similarly, if a TM and/or a subframe type is changed from the DMRS-basedTM and/or the MBSFN subframe to the CRS-based TM and/or the non-MBSFNsubframe, then precoding information may be implemented. Therefore, adefault state for the precoding information may be predefined or may beindicated by the BS to the UE through higher layer signaling and/orphysical layer signaling. In addition, information of DCI receivedduring scheduling of the latest CRS-based TM and/or the non-MBSFNsubframe may be reused.

In some implementations, repeated transmissions for a specific TB may belimitedly performed only within subframes configured as the same type orwithin a single subframe.

For example, referring back to the example of FIG. 14, TTIs #n, #n+1,#n+2, and #n+3 (in which repeated transmissions of data are performed)may be located only in subframes of the same type. In other words,repeated transmissions for a specific data TB may be performed oversubframes having the same type, and may not be performed over subframeshaving different types. Alternatively, repeated transmissions for aspecific TB may be performed only in a single subframe. For example, theUE may not expect that DCI transmitted in the last TTI in a subframewill indicate the number of repeated transmissions of data exceeding 1.

Alternatively, the BS may configure repeated transmissions for aspecific TB over a subframe boundary for the UE, and the BS mayconfigure the same TM and/or the same type for subframes before or afterthe subframe boundary. In terms of the UE, if repeated data transmissionis configured or indicated, then the UE may expect that respective TMsand/or types of subframes in which repeated data transmission isperformed will not be differently configured and will be equallyconfigured.

The UE may assume that a TM associated with detected DCI, i.e., that aTM related to a subframe in which the detected DCI is transmitted and/ora subframe type is applied to all TTIs in which data is repeatedlytransmitted. In other words, if repeated data transmission is indicatedthat it is spanned in subframes, then the UE may assume that data istransmitted based on the same TM and/or the same subframe type in allTTIs corresponding to repeated data transmission. Alternatively, ifrepeated data transmission spans a subframe boundary at which the TMand/or the subframe type is changed (according to the number of repeateddata transmissions configured by the DCI), then the repeated datatransmission is performed only up to a subframe before the subframeboundary and repeated data transmission may be stopped in a subframeafter the subframe boundary. In other words, if a configured duration ofrepeated data transmission spans the subframe boundary at which the TMand/or the subframe type is changed, then it is interpreted that datawhich should be transmitted in a subsequent subframe may be dropped.

In this case, even if the number of repeated transmissions remains,since the UE does not expect that data will be received in a subsequentsubframe, the UE does not perform a data decoding operation in thesubsequent subframe. Therefore, it is unnecessary for the UE to receiveadditional information for decoding the repeatedly transmitted data in asubsequent subframe having a changed TM and/or subframe type. Therefore,if the UE decodes DCI for repeated transmission once, then anexceptional operation of an operation for discarding or not decoding theother DCI need not be defined. In addition, in some scenarios, ambiguitymay be avoided in regards to decoding the repeatedly transmitted data inthe subsequent subframe based on DCI received in a previous subframe.

In some implementations, if the number of repeated data transmissions isconfigured for the UE through DCI, then the number of repetitions may becounted only for TTIs included in a subframe having the same TM and/orsame subframe type as a subframe to which a TTI in which the DCI istransmitted belongs. For example, if subframes are sequentiallyconfigured as a non-MBSFN subframe, an MBSFN subframe, and a non-MBSFNsubframe, and if the number of repeated transmissions configured in thefirst non-MBSFN subframe exceeds the first non-MBSFN subframe, then thenumber of repeated data transmissions may not be counted in the MBSFNsubframe and may be counted in the subsequent non-MBSFN subframe. Thatis, if DCI indicating repeated data transmission is detected in thefirst non-MBSFN subframe, then data indicated to be repeatedlytransmitted may not be transmitted in the MBSFN subframe and repeateddata transmission may be resumed in the subsequent non-MBSFN subframe.

The BS may indicate, to the UE, which of the above-describedimplementations is applied, for example through higher layer signalingand/or physical layer signaling.

As such, if TMs and/or subframe types of subframes are changed andrepeated data transmission is performed over those subframes, then theBS may indicate, to the UE (through higher layer signaling and/orphysical layer signaling), whether to (i) stop a repeated datatransmission operation and drop the remaining repeated transmission, or(ii) count the number of repeated transmissions only in subframes havingthe same subframe type and/or same TM to skip a subframe configured as adifferent subframe type or a different TM while data is repeatedlytransmitted and resume repeated data transmission in a subsequentsubframe having the same type and/or same TM.

In some implementations, if repeated transmission for a specific TB isperformed and a subframe type is changed from a subframe of type A to asubframe of type B, then a combination of one or more of theabove-described implementations may be limitedly applied and, when asubframe type is changed from type B to type A, an operation accordingto an additional rule may be performed.

For example, if a subframe type is changed from an MBSFN subframe to anon-MBSFN subframe while repeated transmission for a specific TB isperformed, then an RS (e.g., DMRS) for decoding TM-based data configuredin the MBSFN subframe may be transmitted as an exceptional case forrepeated data transmission in the non-MBSFN. In other words, a TMrelated RS configured in the MBSFN subframe may be interpreted as beingadditionally transmitted in the non-MBSFN subframe regardless of a TMconfigured in the non-MBSFN subframe.

In some implementations, the above operation may not be applied to thecase in which the same TM is configured in subframes (even if the typesof subframes are changed) and instead may be applied to the case inwhich a different TM is configured per subframe or subframe type.

Alternatively, in some implementations, even if the type and/or TM ofthe subframe is changed while data is repeatedly transmitted, the sameconfiguration of a type and/or TM of a front subframe may be appliedwhile the data is repeatedly transmitted.

For example, while data is repeatedly transmitted, if a TM and/or asubframe type is changed from a DMRS-based TM and/or an MBSFN subframeto a CRS-based TM and/or a non-MBSFN subframe, then the DMRS-based TMmay be maintained in a TTI in which the data is repeatedly transmittedor the DMRS-based TM may be maintained in all of the non-MBSFN subframe,as an exceptional case. As another example, while data is repeatedlytransmitted, if a TM and/or a subframe type is changed from theCRS-based TM and/or the non-MBSFN subframe to the DMRS-based TM and/orthe MBSFN subframe, then this may be addressed through networkscheduling or a TM for repeated transmission may be semi-staticallyconfigured separately from a TM for another subframe set.

FIG. 15 shows an example of a radio communication apparatus according tosome implementations of the present disclosure.

The wireless communication apparatus illustrated in FIG. 15 mayrepresent a User Equipment (UE) and/or a base station (BS) according toan implementation of the present disclosure. However, the wirelesscommunication apparatus of FIG. 15 is not necessarily limited to the UEand/or the BS according to the present disclosure, and may implementvarious types of apparatuses, such as a vehicle communication system orapparatus, a wearable apparatus, a laptop, etc.

In the example of FIG. 15, a UE and/or a B S according toimplementations of the present disclosure includes at least oneprocessor, such as processor 10, which may include, for example, adigital signal processor or a microprocessor. The UE and/or BS alsoincludes a transceiver 35, a power management module 5, an antenna 40, abattery 55, a display 15, a keypad 20, at least one memory 30, asubscriber identity module (SIM) card 25, a speaker 45, and a microphone50, and the like. The UE and/or the BS may include a single antenna ormultiple antennas. The transceiver 35 may be also referred to as an RFmodule.

The at least one processor 10 may be configured to implement thefunctions, procedures and/or methods described in FIGS. 1 to 14. In atleast some of the implementations described in FIGS. 1 to 14, the atleast one processor 10 may implement one or more protocols, such aslayers of the air interface protocol (e.g., functional layers).

The at least one memory 30 is connected to the at least one processor 10and stores information related to the operation of the at least oneprocessor 10. The at least one memory 30 may be internal or external tothe at least one processor 10 and may be coupled to the at least oneprocessor 10 via a variety of techniques, such as wired or wirelesscommunication.

The user can input various types of information (for example,instruction information such as a telephone number) by varioustechniques such as pressing a button on the keypad 20 or activating avoice using the microphone 50. The at least one processor 10 performsappropriate functions such as receiving and/or processing information ofthe user and dialing a telephone number.

It is also possible to retrieve data (e.g., operational data) from theSIM card 25 or the at least one memory 30 to perform the appropriatefunctions. In addition, the at least one processor 10 may receive andprocess GPS information from the GPS chip to obtain location informationof the UE and/or BS such as vehicle navigation, map service, or thelike, or perform functions related to location information. In addition,the at least one processor 10 may display these various types ofinformation and data on the display 15 for reference and convenience ofthe user.

The transceiver 35 is coupled to the at least one processor 10 totransmit and/or receive radio signals, such as RF signals. At this time,the at least one processor 10 may control the transceiver 35 to initiatecommunications and transmit wireless signals including various types ofinformation or data, such as voice communication data. The transceiver35 may comprise a receiver for receiving the radio signal and atransmitter for transmitting. The antenna 40 facilitates thetransmission and reception of radio signals. In some implementations,upon receipt of a radio signal, the transceiver 35 may forward andconvert the signal to a baseband frequency for processing by the atleast one processor 10. The processed signals may be processed accordingto various techniques, such as being converted into audible or readableinformation, and such signals may be output via the speaker 45.

In some implementations, a sensor may also be coupled to the at leastone processor 10. The sensor may include one or more sensing devicesconfigured to detect various types of information, including velocity,acceleration, light, vibration, and the like. The at least one processor10 receives and processes the sensor information obtained from thesensor such as proximity, position, image, and the like, therebyperforming various functions such as collision avoidance and autonomoustravel.

Meanwhile, various components such as a camera, a USB port, and the likemay be further included in the UE and/or the BS. For example, a cameramay be further connected to the at least one processor 10, which may beused for a variety of services such as autonomous navigation, vehiclesafety services, and the like.

FIG. 15 merely illustrates one example of an apparatuses constitutingthe UE and/or the BS, and the present disclosure is not limited thereto.For example, some components, such as keypad 20, Global PositioningSystem (GPS) chip, sensor, speaker 45 and/or microphone 50 may beexcluded for UE and/or BS implementations in some implementations.

Specifically, in order to implement implementations of the presentdisclosure, an operation when the radio communication apparatusillustrated in FIG. 15 is a UE according to an implementation of thepresent disclosure will now be described. When the radio communicationapparatus is the UE according to an implementation of the presentdisclosure, the processor 10 may control the transceiver 35 to receivefirst information for configuring types of subframes and secondinformation for configuring TMs applied to the subframes through higherlayer signaling and/or physical layer signaling. Next, the processor 10decodes DCI related to repeated transmission of data in a specific TTI,specifically, in an sTTI. The DCI may include information about thenumber of repeated transmissions of the data and information about anMCS, RA, precoding, and rank, for a type and a TM configured in asubframe in which the DCI is included.

Upon detecting the DCI, the processor 10 may control the transceiver 35to receive repeatedly transmitted data over subframes configured asdifferent types and/or different TMs, based on the information includedin the DCI, the first information, and the second information.

A detailed operation method of receiving the repeatedly transmitted dataover subframes by the processor based on the detected DCI, the firstinformation, and the second information may conform to theimplementations described with reference to FIGS. 1 to 14.

In order to implement implementations of the present disclosure, whenthe radio communication apparatus illustrated in FIG. 15 is the BSaccording to an implementation of the present disclosure, the processor10 may control the transceiver 35 to transmit first information forconfiguring types of subframes and second information for configuringTMs applied to the subframes through higher layer signaling and/orphysical layer signaling. Next, the processor 10 control the transceiver35 to transmit DCI related to repeated transmission of data in aspecific TTI, specifically, in an sTTI. The DCI may include informationabout the number of repeated transmissions of the data and informationabout an MCS, RA, precoding, and rank, for a type and a TM configured ina subframe in which the DCI is included.

The processor 10 for control transmission of the DCI may control thetransceiver 35 to transmit repeatedly transmitted data in subframesconfigured as different types and/or different TMs, based on theinformation included in the DCI, the first information, and the secondinformation.

A detailed operation method of transmitting the repeatedly transmitteddata by the B S in subframes configured as different types and differentTMs based on the transmitted DCI, the first information, and the secondinformation may conform to the implementations described with referenceto FIGS. 1 to 14.

The implementations described above are those in which the elements andfeatures of the present disclosure are combined in a predetermined form.Each component or feature shall be considered optional unless otherwiseexpressly stated. Each component or feature may be implemented in a formthat is not combined with other components or features. It is alsopossible to construct implementations of the present disclosure bycombining some of the elements and/or features. The order of theoperations described in the implementations of the present disclosuremay be changed. Some configurations or features of certainimplementations may be included in other implementations, or may bereplaced with corresponding configurations or features of otherimplementations. It is clear that the claims that are not expresslycited in the claims may be combined to form an implementation or beincluded in a new claim by an amendment after the application.

The specific operation described herein as being performed by the BS maybe performed by its upper node, in some cases. That is, it is apparentthat various operations performed for communication with a UE in anetwork including a plurality of network nodes including a BS can beperformed by the BS or by a network node other than the BS. ABS may bereplaced by terms such as a fixed station, a Node B, an eNode B (eNB),an access point, and the like.

Implementations according to the present disclosure may be implementedby various means, for example, hardware, firmware, software or acombination thereof. In the case of hardware implementation, animplementation of the present disclosure may include one or moreapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs) field programmable gate arrays,processors, controllers, microcontrollers, microprocessors, and thelike.

In the case of an implementation by firmware or software, animplementation of the present disclosure may be implemented in the formof a module, a procedure, a function, or the like for performing thefunctions or operations described above. The software code can be storedin a memory unit and driven by the processor. The memory unit may belocated inside or outside the processor, and may exchange data with theprocessor by various well-known means.

While the above-described method of transmitting and receiving a DL datachannel and the apparatus therefor have been described focusing upon anexample applied to the 3GPP LTE system, the present disclosure isapplicable to various wireless communication systems in addition to the3GPP LTE system.

According to the present disclosure, data which is repeatedlytransmitted in subframes configured as different subframe types and/ordifferent TMs can be efficiently transmitted and received

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other advantages of thepresent disclosure will be more clearly understood from the abovedetailed description taken in conjunction with the accompanyingdrawings.

It will be apparent to those skilled in the art that the presentdisclosure may be embodied in other specific forms without departingfrom the spirit of the disclosure. Accordingly, the above descriptionshould not be construed in a limiting sense in all respects and shouldbe considered illustrative. The scope of the present disclosure shouldbe determined by rational interpretation of the appended claims, and allchanges within the scope of equivalents of the present disclosure areincluded in the scope of the present disclosure.

What is claimed is:
 1. A method for transmitting a downlink data by abase station (BS) in wireless communication system, the methodcomprising: transmitting Downlink Control Information (DCI) forscheduling repeatedly transmission of the downlink data in at least onefirst Short Transmission Time Interval (sTTI) included in a firstsubframe and at least one second sTTI included in a second subframe,transmitting, based on the DCI, repeatedly the downlink data in the atleast one first sTTI and the at least one second sTTI only based on afirst transmission mode for the first subframe and a second transmissionmode for the second subframe being identical, wherein the secondsubframe is after the first subframe.
 2. The method of claim 1, whereinthe downlink data is transmitted only in the at least one first sTTIbased on the first transmission mode and the second transmission modebeing different.
 3. The method of claim 1, wherein the downlink data isnot transmitted in the at least one second sTTI based on the firsttransmission mode and the second transmission mode being different. 4.The method of claim 1, wherein the first subframe and the secondsubframe are consecutive.
 5. The method of claim 1, wherein a number ofrepeatedly transmitted of the downlink data is greater than
 1. 6. A basestation (BS) for transmitting a downlink data in wireless communicationsystem, the BS comprising: at least one transceiver; at least oneprocessor; and at least one memory operably connectable to the at leastone processor and storing instructions that, when executed by the atleast one processor, perform operations comprising: transmitting, viathe at least one transceiver, Downlink Control Information (DCI) forscheduling repeatedly transmission of the downlink data in at least onefirst Short Transmission Time Interval (sTTI) included in a firstsubframe and at least one second sTTI included in a second subframe,transmitting, via the at least one transceiver, repeatedly the downlinkdata, based on the DCI, in the at least one first sTTI and the at leastone second sTTI only based on a first transmission mode for the firstsubframe and a second transmission mode for the second subframe beingidentical, wherein the second subframe is after the first subframe. 7.The BS of claim 6, wherein the downlink data is transmitted only in theat least one first sTTI based on the first transmission mode and thesecond transmission mode being different.
 8. The BS of claim 6, whereinthe downlink data is not transmitted in the at least one second sTTIbased on the first transmission mode and the second transmission modebeing different.
 9. The BS of claim 6, wherein the first subframe andthe second subframe are consecutive.
 10. The BS of claim 6, wherein anumber of repeatedly transmitted of the downlink data is greater than 1.11. A computer readable storage medium storing at least one computerprogram comprising instructions that, when executed by at least oneprocessor, cause the at least one processor to perform operations, theoperations comprising: transmitting Downlink Control Information (DCI)for scheduling repeatedly transmission of the downlink data in at leastone first Short Transmission Time Interval (sTTI) included in a firstsubframe and at least one second sTTI included in a second subframe,transmitting, based on the DCI, repeatedly the downlink data in the atleast one first sTTI and the at least one second sTTI only based on afirst transmission mode for the first subframe and a second transmissionmode for the second subframe being identical, wherein the secondsubframe is after the first subframe.